0020715: AI to start with 3 Guardians, unlock more with AIP as in Classic

Description

Currently, it can send any of them for anything. This sadly means that it is doing a "jack of all trades master of none" - there's no reason to counter any in particular, because there are never enough of one type to pose a specific threat, and they also never get enough of any one type to counter anything of yours.

As noted by zeusalmighty in Discord, he has a concern about them being too confusing to new players - limiting how many the AI starts with may make it...simpler, to understand, instead of having all of them appearing everywhere.

I hope this'd make them more interesting. Just something that came in discussion with zeusalmighty.